The invention concerns a device for measuring the width and/or position of a metal strip or slab, which has at least two measuring systems, one on each side of the metal strip or slab, where each measuring system has a sensor designed to detect the lateral edge of the metal strip or slab.
The width of strips is often measured by contactless methods, e.g., optically by photoelectric cells or cameras arranged vertically above the strip and especially near the edge of the strip. Another possible means of determining the lateral edge of a metal strip or a slab is by radiometry. Mechanical measurement by means of a measuring roller is also well known. In this method, the deflection of the measuring roller transverse to the longitudinal direction of the metal strip or slab is determined. Strips are measured both in cold rolling mills and hot rolling mills.
Measurement of the width of the strip or slab before the edging process in a conventional hot strip mill is especially important. The width of the strip or slab is the input variable for the automatic width control. A functional automatic width control system in turn is a critical entity for the geometric quality of the hot strip and thus also has a corresponding influence on the economy of a hot strip mill.
A device of this general type is disclosed, for example, in GB 2 138 180 A. A metal strip to be rolled passes through a rolling stand, and sensors for determining the position of the lateral edges of the strip are arranged on both sides of the lateral edges of the metal strip. In one embodiment, these sensors are mounted in a stationary position, and an optical system is used to detect the lateral edge of the metal strip. In another embodiment, a roller rests against the lateral edge of the strip and is mounted in such a way that it can move in the direction transverse to the longitudinal axis of the metal strip against the force of a spring. The deflection of the roller is measured, and this makes it possible to infer the position of the location of the lateral edge of the metal strip. Two measuring systems of this type can cooperate with each other to determine the width of the strip.
Another solution is known from DE 31 16 278 A1. In this case, a roller that is set against the edge of the strip is provided on both sides of the metal strip. The roller is mounted on an elastic arm, which allows a deflection of the roller in the direction transverse to the longitudinal axis of the metal strip. Strain gauges are mounted on the elastic arm in such a way that when the arm is deflected, it is possible to infer the deflection of the roller and thus, when two such measuring systems are used, to infer the strip width.
EP 0 166 981 B1 describes a positioning control device for guide plates or guide rollers, which are mounted in such a way that they can be displaced transversely to the rolling direction of a metal strip or slab. The displacement of the guide plate or guide roller is carried out automatically.
Another solution for adjusting lateral guide elements for a metal strip in a rolling installation is described in EP 0 925 854 A2. In this case, sensors that can measure the distance of the guide element from the edge of the strip are integrated in the guide elements. JP 61[1986]-108,415 A discloses a similar solution.
According to EP 1 125 658 A1, stationary gap sensors are used to determine the position of the edge of a continuously cast metal strip or slab.
Sensors for measuring the thickness of the rolled strip or the slab in a rolling installation are disclosed by JP 63[1988]-194,804 A, which describes measuring rollers that lie on the upper side and the underside of the rolled product. The use of measuring rollers of this type is also known from JP 63[1988]-194,803 A.
JP 63[1988]-010,017 A describes a system in which measuring rollers adjacent to the edges of the strip are equipped with a sensor, which, as the roller approaches the edge of the strip, reduces the approach speed in time to prevent the measuring roller from damaging the edge of the strip. The manner in which measuring roller is moved up to the strip edge is not described in detail.
The ambient conditions during the width measurement of a near-net strip in the vicinity of an edger or a slab upsetting press are characterized by high temperatures, heavy scale production, cooling water, steam, strong vibrations, etc. These ambient conditions can cause breakdowns or measuring errors with the conventional measuring principles that are employed, because, for example, scale, water, etc., can be deposited on cameras and photoelectric cells. Strong vibrations arising from the production process can affect or damage the electronics of the installation.
This leads to a preference for mechanical measuring systems, especially measuring rollers. It is necessary—of course, not just in this case, but especially in this case—that the width of the metal strip or slab can be determined in a very dynamic way, i.e., the ability of the sensors to move in the direction transverse to the longitudinal direction of the metal strip or slab must be marked by high speed if an optimum measurement result is to be obtained.
Naturally, however, due to the harsh ambient conditions, a robust mode of operation of the device must be guaranteed.
All previous solutions have had to accept limitations in this respect.
Therefore, the objective of the invention is to further develop a device of the aforementioned type in such a way that the disadvantages cited above are avoided or at least reduced. The device for measuring the width and/or the position of the metal strip should operate very robustly and highly dynamically and should be insensitive to ambient conditions.